Take a look at the Lifeline AGM starter batteries:
Lifeline Batteries - Marine & RV Deep Cycle Batteries
32 lbs and 850cca

Paul L

 

Charging a starting battery really is not a consideration for the alternator. The energy needed to start a motor is tiny compared to a house bank, and the energy is replaced very quickly, unless you are labouring the starter motor.

 

The starter is 1000watts and at 12V that is 83amps + some loss. Let's call it 90 amps of current. A 240MCA battery can sustain 240amps for 30 seconds before becoming TOTALLY dead. I think you will be cutting it very close with that battery especially since 3GM's have a rep for being difficult to start. Does yours take a while to get it to turn over?
If you want to try this....Sears has a Gold diehard garden tractor U1 size with 340CCA's (more stringent than MCA's) that may give you a bit more margin for error.

 

Okay, I sort of knew this answer was coming. Thanks for the feedback. I guess I won't share my idea to wire together 8 AAA Energizers!

No, our engine starts fairly easily (except in sub 40 F -- no glow plugs), but I still would not want to cut it that close.

Take a look at the Lifeline AGM starter batteries:
Lifeline Batteries - Marine & RV Deep Cycle Batteries
32 lbs and 850cca Paul L

Paul, thanks for that link, I wasn't aware of that particular Lifeline starting battery. Dimensionally it's fairly close to the standard U1 form factor, but with a lot more output. Anyone tried this battery? Cam, thoughts? Our current Lifeline AGMs have given us great service.

Rockter, I'm at 55 amps (nominally) alt output with a 220-230 ah house bank already. But you're probably right, I normally won't be drawing this starting battery down like the house bank. Hopefully the larger size won't over tax the charging capability of the alternator..

 

Not a place to skimp.

 

There are some smaller batteries than the 24 that are as powerfull. Most of the new cars have smaller batteries as will as 100+ altinators.
Groups 56 and 72 come to mind.

 

Interesting

I guess I am very different. I use a 12 Volt Battery. Guess that Scary today for me, when mine getting weak at 9 years old and out of warranty!

There are $50 batteries out there that last 9 years for the money???? With proper care.

I interested now! Very good question.

Damn, woman says I should add something. I not know, maybe buy a sailboat???? But, I not use much of a battery on a sailboat????

I have had motorboats? but, that different!

 

Gryz...the batteries we are discussing ARE 12V batteries...just different sizes and cranking power.

JRP... that Lifeline looks pretty good to me. The MCA of 550 (MCA=CCA @ 0 degrees F) ...is pretty close to the Group 24 and if you have no problems with the 24 then I'd say it is worth a shot if you can fit it.
I would NOT worry about your charging capacity from the alternator at all. Starting will take 90 amps for 15 seconds or so...which means less than ONE amp hour to be replaced. Even a whole minute of starting is only 1.5 amp hours! About the same as running a cabin light for an hour!!

 

Thanks again everybody -- very helpful.

Cam, I am inclined to try that Lifeline GPL 1400T that Paul linked to. It prices out at $180 (BD Batteries - delivered) which is steep for a battery of this size (I paid about that price for our Grp 31s albeit 5 years ago -- looks like prices have gone way up). But given their track record on our boat, I know Lifelines represent good value.

I had toyed with the idea of doing some R&D with an Odyssey battery like the PC1200 ( PC 1200 Deepcycle Odyssey Battery, Marine Heavy Duty Battery, Diesel, Trolling Motors - Odyssey Drycell Batteries ), but I haven't found a price for them yet. I expect it will be pricier than the Lifeline, and I really need to cap out the costs of this project....

 

At what temperature do you need to crank the engine - in cold weather you will need to choose a much bigger battery

 

For the most part, we are operating in temps above 50 F, and the vast majority of the time above 65 F. Occasionally, during early spring and late fall, we will be running in temps lower than 50 F, but we now have a cabin heater and interior ambient temps would rarely be lower than 60 F.

This Lifeline GPL1400T seems to have about 83% MCA rating as a Group 24. For really cold weather, I would have the system set-up so I could bridge over to the house bank (2 x Grp 31) if necessary.

 

JRP...the Odyssey 1200's are NOT much more than the Lifelines.
Odyssey Batteries and price list

 

Thanks for that price list, Cam. I somehow missed it on their site.

$192 + shipping for the Odyssey. Since the BD price on the Lifeline includes shipping, the Odyssey will probably come out about $35-40 over the Lifeline. Another factor is that it weighs about 6 lbs more. Not a big deal, but I'm going to be dangling upside down to install this thing, so every bit matters....

 

JRP...Funny...I had looked at the Odysseys compared to wet cells in price and said "holy xxxx" those are expensive" ...compared to the Lifelines though they aren't bad. If they do what they say...that should put a lot of price pressure on Lifeline, Rolls, Optima etc. etc.
I don't think there is much advantage for a starter...but house batteries with that price differential would be quite attractive given the many benefits over standard AGM/Gels that are touted.